Interest calculations re. overpayment

I was hoping someone could explain this for me! I can overpay my mortgage by up to 10% every year. In terms of interest calculation on my mortgage, does it matter at what point in the year I do that?
For example, say my mortgage was taken out 1st July 2019. One year later, the 10% I can overpay is reset. So does it make a difference if I overpay the 10% for the period 2nd July 2020 - 1st July 2021 as an ongoing amount every month, or is it better to pay the full 10% off on 2nd July 2020? For instance, do I still pay same interest figure on my mortgage if I overpay the 10% off on 30th June 2021 compared with paying it 2nd July 2020?
I did phone my bank’s mortgage line and ask this but they didn’t seem to understand the question, and just kept repeating that I could only overpay by 10% in a year. I may have not articulated it very well...


  • [Deleted User]
    [Deleted User] Posts: 35,242 Forumite
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    Interest is calculated daily, so the lower your balance, the less interest you pay.
  • jenni_fer
    jenni_fer Posts: 529 Forumite
    First Anniversary First Post Name Dropper
    For most (if not all these days) mortgages the interest will be calculated daily so the sooner you make the overpayment the more interest you save.
  • Mrs_Rachel_Trelfa
    Just check that the per year refers to calander year (i.e 1st January to 31st December) and not yearly based on when your mortgage starts. If interest is calculated daily the as soon as possible. 
    House purchased November 2013
    Original MF Date: January 2045 - £104,400
    Current MF Date: April 2030- £48,719. 75
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